Nicole S.

asked • 09/28/18

i NEED HELP. Question about Trigonometry.

In isosceles triangle ABC, AB=AC=7cm and angle A=56. I need to calculate BC

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Paul M. answered • 09/28/18

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BS Mathematics, MD
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This is a straight application of the law of cosines!
The square of BC = 72 + 72 - 2*7*7 cos 56°
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Nicole S.

I didn't understand what should i do! help pls!
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09/28/18

Paul M.

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You can do it another way. Draw a figure & draw the perpendicular bisector of the base. Now you have 2 congruent right triangles. The hypotenuse is 7 & the angle at the apex is 28 degrees. 1/2 of the base is 7 times sin 28.
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09/28/18

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